The present invention relates generally to self-processing photographic cameras of the reflex type and, more particularly, to a reflex camera in which a specular surface is moved into the optical path of a taking lens when the camera is caused to assume an exposure mode configuration.
Certain photographic film materials are structured to directly record a positive image of any subject properly imaged and exposed thereon. Exemplary of such materials are the film units described in U.S. Pat. No. 3,415,644, entitled "Novel Photographic Products and Processes" and issued to E. H. Land on Dec. 10, 1968. Film units of this type are intended for use within the above-noted self-processing photographic cameras and incorporate all of the materials necessary to produce a positive photographic print immediately following their exposure. While being of a somewhat complex chemical makeup, the film units are physically structured to include a planar photosensitive element in laminar combination with a transparent image-receiving element. Specially packaged processing units are additionally included within the unit.
To image properly through a lens system upon the above-described film units, it is necessary that one or an odd number of specular surfaces be incorporated within the optical path extending from the camera lens to the exposure plane of the film unit. Although the film units are configured to provide a desirably large film format, certain improved photographic camera designs have taken advantage of the requisite specular surface to achieve somewhat compact overall camera structures.
Improved photographic cameras as above described are intended to perform in fully automated fashion while being structured so thinly and compactly as to be carried conveniently in the pocket of a garment. Typically, these improved cameras incorporate an optimum viewing and focusing system together with fully automatic exposure control and motorized automatic film processing. In effect, the fully automatic camera represents an instrumentality incorporating a complex, multi-step process control system.
For purposes providing optimum viewing performance as well as structural compactness, the automated camera preferably utilizes a form of single lens reflex viewing. As described and claimed in U.S. Pat. No. 3,672,281, entitled "Reflex Camera", and issued to E. H. Land on June 27, 1972, such reflex cameras normally assume a viewing-focusing mode configuration in which their exposure plane is isolated from scene illumination by a flat movable operator or mirror and viewing surface assembly. In a viewing configuration, the operator assembly serves a function of providing a surface upon which a scene, in reflex fashion, may be framed and focused in preparation for a photographic exposure. In accordance with a modified single lens optical operation, depression of a start button on the camera commences a multi-step control causing its components to assume an orientation securing an exposure chamber by closing its shutter through an electromagnetic drive system. When this chamber is secured, the camera is caused to commence an exposure mode operation in which the earlier-described operator assembly is released for movement via a spring drive to uncover the exposure plane and provide a revised reflex optical path for subsequent exposure of the previously imaged scene.
As an exposure mode configuration is achieved, the automatic exposure control sub-system of the camera cycles through a regulated exposure interval following which the shutter again closes to secure the exposure chamber. The control system of the camera is then called upon to cock the operator assembly by driving it, via an electrical motor, into its viewing mode configuration. Prior to termination of the photographic cycle, an exposed photosensitive film unit is automatically removed from its position at the exposure plane and drawn through a motor-driven processing station. When the operator assembly has been cocked and returned to its orientation covering the exposure plane, the shutter is again opened to its maximum extent and the camera is ready for its next succeeding photographic cycle.
As mentioned previously, the operator assembly is cocked by driving it via an electrical motor into its viewing mode configuration. As a consequence, the operator assembly drive system will usually require an override form of drive linkage to assure proper seating at its cocked position. Such override feature is extremely difficult to incorporate within the confined housings of compact cameras without resorting to the use of relatively high-torque rate drive springs with their attendant undesirably high loads on the relatively small drive motor.
If the operator assembly encounters any interference during its movement toward its cocked or viewing-focusing mode position, the motor may be overloaded and damaged. Certainly, if the motor is overloaded enough, the power drain upon a power supply such as a battery may render it incapable of carrying out other functions during a given photographic cycle.
In dealing with some of the foregoing problems, certain novel photographic cameras such as described in copending application Ser. No. 246,854, filed Apr. 24, 1972, now U.S. Pat. No. 3,760,703, and commonly assigned herewith, incorporate a lost-motion connection within the drive system for moving the operator assembly between the exposure mode position and the viewing mode position. Movement of the operator assembly between these positions is accomplished through a system incorporating a four bar linkage and drive spring means. The system is configured to minimize the time required for moving the operator assembly to its exposure mode position whilst also minimizing the elastic rebound of the operator assembly when it reaches its exposure mode position.
A torsion spring and tension spring adapted to deliver a substantially uniform torque are employed for moving the operator assembly to its exposure mode position. The springs are preloaded to minimize the operator assembly movement time and also reduce its elastic rebound upon reaching the exposure mode position. This is achieved by maximizing the residual torque of the drive springs at the exposure mode position of the operator assembly.
A pair of preloaded override tension springs are provided within the drive system and serves to provide an override or lost-motion connection between the motor and the operator assembly. If the operator assembly encounters any interference during its motor-driven movement between the exposure and viewing mode positions, the override springs will allow the motor to finish its normal return cycle. The energy from the motor will be transferred to and stored in the override springs until such time as the interference is removed. When the interference is removed, the override springs return the operator assembly to its viewing position and any overload or attendant damage to the motor will be eliminated.
The employment of the override springs insures proper positioning and seating of the reflecting member at its viewing position where it protects the unexposed photosensitive material. However, the problem of properly protecting the photosensitive material reoccurs if the camera is abused or roughly handled. Should the camera be sharply jostled or bounced, the override springs may not be of sufficient strength to retain the reflecting member in its film protecting position. As a result, ambient light may reach the uncovered film unit and cause either partial or total exposure of the film unit. Accordingly, some method of assuring proper film protection during this period would be most desirable. Such a method should not interfere with normal camera operation and ideally should only be operational during periods of unusual stress.
Copending application Ser. No. 222,964, filed on Feb. 2, 1972, in the name of I. Blinow, now U.S. Pat. No. 3,714,427 and entitled "Reflex Camera with Mirror Latch", is addressed to a latching arrangement for use within a photographic apparatus employing a reflecting member movable to convert an optical path between viewing and exposure configurations. The latching arrangement both establishes latching association with the reflecting member for securing the same at a seated viewing position and is movable out of latching association at the commencement of a photographic cycle for permitting the release of the reflecting member.
Providing a safety feature, the latching arrangement assures that the reflecting member is retained in its seated viewing position should the camera be jostled or bounced. The latching arrangement thus serves to assure that film units within the camer are not inadvertently exposed. The latching association is discontinued during an initial phase of a photographic cycle to permit release of the reflecting member for spring driven movement toward its exposure position.
A motorized control mechanism forming part of the camers's control system operates to release the reflecting member for the noted spring-driven movement. Following a photographic exposure, the motorized control mechanism returns and cocks the reflecting member at its seated viewing position. Latching association is only then reestablished as the photographic cycle ends.
A lost-motion linkage is operatively associated between the reflecting member and motor drive for permitting an incremental amount of motor operation following the return of the reflecting member to its viewing position. An overtravel spring, formed as part of this lost-motion linkage assembly, operates as an energy storing element during the continued operation of the motor. This stored energy within the overtravel spring is employed to retain the reflecting member in its viewing position. Should the overtravel spring be of insufficient strength to retain the reflecting member in its viewing position during camera abuse, the latching arrangement remains operative to do so.
It has been found, however, that a latching arrangement such as described in application Ser. No. 222,964, aforesaid, is subject to malfunction due to the complexity of its assembly.
The latching means includes a timing gear within the motor control mechanism to which a profile cam is secured. An actuator member is spring biased into engagement with the profile cam and, in turn, drives a latch member which is slideably carried by the camera frame and is capable of engaging a docking assembly.
Obviously, the complex interaction of such a member of components is not only susceptible to operating malfunction, but there is the added complication and expense of assembly in addition to parts cost.